Is the DDF part of the reciprocal apparatus?

• A. True
• B. False
• C. Only in Hind Limbs
• D. Only in Forelimbs

Answer: (B)

The stay apparatus relies on a cross-joint linkage that coordinates the movement of joints along the limb, so when one joint moves, the connected joint follows. In the common description of this mechanism, the parts that create that link are muscles and tendons like the peroneus tertius and the superficial digital flexor tendon, which tie the actions at the joints across the stay apparatus. The deep digital flexor tendon, by contrast, is a distal flexor of the digits—it runs to the distal phalanx and bends the hoof, but it does not participate in the cross-joint linkage that coordinates stifle and carpus (or hock) movements. Because of that, the DDF is not part of the reciprocal apparatus.